Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 132119
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
319 PM MDT Sun Aug 13 2017

.SYNOPSIS...

A cold front will bring scattered showers and isolated
thunderstorms to much of the area this afternoon along with a
period of gusty winds. This front will continue to bring areas of
smoke into the area from fires in the area. Thunderstorms linger
across Southwest Montana into Monday, but gradual clearing is
expected across central Montana.

&&

.DISCUSSION...

Rest of today through tonight...Latest water vapor shows a potent
shortwave encroaching on the northern Rockies at this time. Ahead
of it, a band of showers continues to progress east across
northern Idaho/western MT. Ahead of this band, scattered showers
and isolated thunderstorms have begun developing across much of
central/SW MT. Instability continues to look weak, and the overall
coverage and strength of thunderstorms looks a bit lower than
originally forecast. The strength of storms looks in question as
well with the lack of better instability. To the west, several
surface obs have been reporting gusts of 20-30 mph associated with
the front and that will likely continue as the front pushes east.
The strongest winds with the front looks to be along/west of a
Chester to Great Falls line with somewhat lower gusts as it pushes
east. The front then slows down some tonight across our far
eastern counties and south through SW MT. Lingering moisture/lift
should keep showers and a few thunderstorms going there longer.
MARTIN

Monday through Tuesday...We begin to see an end to the widespread
rain coverage early Monday morning, with our area remaining in a
persistent southwesterly flow aloft. Broadscale trough and lingering
moisture will allow for chances of showers and thunderstorms to
continue for Monday, mainly be for southern and some eastern areas.
Tuesday will feature continued drying conditions with continued near-
seasonal temperatures. Lingering moisture across the south my once
again bring a few isolated to scattered showers and thunderstorms
for these areas.

Tuesday night through Sunday...We stay in a quasi-zonal upper-
level flow aloft as we get into the middle part of the week. A
passing weak disturbance may ignite some isolated showers or storms
Thursday, however, coverage will remain limited. We return to a weak
ridging pattern aloft by late week and into the weekend with the
potential for dry weather and moderating temperatures back to
slightly above-normal. Fortunately, there continues to be no sign of
any extreme heat returning in the foreseeable future.
KLG/Anglin

&&

.AVIATION...
Updated 1800Z.

A cold front is just now approaching the Continental Divide as of
18z. This front will sweep east this afternoon/evening, with an
increased threat of SHRA/TSRA, some with gusty winds in excess of
40kt. Hail cannot be ruled out, but the threat looks lower in
general. A period of gusty winds is also expected with the front,
itself. Lower VIS/CIGs can be expected with any SHRA or TSRA that
moves over a terminal. In addition, smoke continues to pour into
the area as the W/SW flow increases and this has, and likely will
continue to, lead to MVFR VIS at times. Gradual clearing is
expected tonight across central MT, but clouds, SHRA, and a few
TSRA will linger across SW MT potentially into the day Monday.
MARTIN

&&

.FIRE WEATHER...

The main concern over the next 12 to 24 hours is increased
thunderstorm activity followed by a cold front with gusty winds.
Of note, latest trends suggest the lightning activity will not be
quite as widespread as originally thought, but still worth noting
given the recent dry conditions an the incoming front. For these
reasons, we decided to continue the Red Flag Warning through this
evening, but we`ll continue to evaluate conditions and cancel
parts of the warning early if necessary. Beyond this weekend,
drier conditions are expected along with near normal temperatures.
MARTIN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  54  77  48  78 /  40  10  10  10
CTB  51  75  44  75 /  30  10  10  10
HLN  53  78  49  80 /  40  10  10  10
BZN  52  76  48  78 /  50  50  30  20
WEY  43  67  38  68 /  60  50  40  40
DLN  49  76  46  77 /  40  50  20  10
HVR  58  80  51  79 /  60  10  20  10
LWT  55  74  50  75 /  70  20  20  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT this evening Central and Eastern
Lewis and Clark National Forest Areas...Chouteau and Fergus
Counties...Deerlodge/Western Beaverhead National Forest...
Eastern Beaverhead National Forest...Eastern
Glacier/Toole/Central/Eastern Pondera/Liberty...Helena and
Townsend Ranger Districts of the Helena National Forest...Hill
and Blaine Counties...Lewis and Clark National Forest Rocky
Mountain District-Rocky Mountain Front...Lincoln Ranger District
of the Helena National Forest.

&&

$$

weather.gov/greatfalls



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